1st 5K run next weekend (strenth training? cramps?)

Are you eating within a couple of hours of running? Or drinking more fluids before running than usual? And the biggy...are your bowels regular? Could bowels be sending you a sign?
I don't do running and strength on same days.
Running outside is going to be a whole new ballgame. Don't wait until next week to do it, you will possibly hurt in all new areas and you need to be used to and recovered before the race.
Good luck on your 5k!

I used to run on the treadmill only, but running outside is much more fun (even in the polluted city I live in!)… Main tip: take it easy. Your first 5K run should be more fun than a race. See where your limit is and use that as a mark to gradually improve speed and distance.
You don't need any bizarre meals or drinks to finish. Just eat a carb-rich meal some 1.5 hours before and maybe a banana 30 minutes before and when you run, keep a comfortable tempo and breath with a rhythm. Took me a while to find the right pace, but once you do, running becomes really pleasurable.

And oh yea, shoes that fit your feet - not only size but also supination and strike-wise - are really important! (not the ones in your profile pic lol).

Good luck and have fun on your run!